This Week’s Sky at a Glance, April 28 – May 5

When people see an amateur astronomer’s telescope that doesn’t look like it came from a department store, they often have two questions: “How much did that baby cost?” and “How far can you see with that?” The answer to the first is usually about ten times less than they guess, but the answer to the second is difficult to explain and even more difficult to comprehend. Sometimes I just say “way far” and hope they don’t press for details.

On a clear evening this weekend just go outside and look up. The brightest object will be the Moon and it will be about 380,000 kilometres away. Next Saturday it will be at its farthest (apogee) at
405,000 km. The next brightest object is Jupiter, which will be at opposition on May 8 and hence closest to us at a distance of 660 million kilometres. In the morning sky, Mars is currently 130 million km away and Saturn is 1.4 billion km out there. Light travels at 300,000 km/s, so at 150 million km the Sun is a distance 500 light seconds away. The Moon is a tad more than a light second; Jupiter is 36 light minutes and Saturn nearly 80 light minutes.

The brightest star we see in the evening now is still Sirius, the closest star we can see from New Brunswick at 8.6 light years (ly). The next brightest is Arcturus and it is 37 ly or 350 trillion km. Polaris, the North Star, is about 400 ly away; and Alnilam, the middle star of Orion’s belt, is 2000 ly, If you are under a dark sky well before morning twilight you might get a naked eye glimpse of the Andromeda Galaxy at a distance of 2.5 million light years. Yes, a small telescope will reveal things even more distant, but at what point do these distances become incomprehensible and “way far” is a reasonable answer?

This Week in the Solar System

Saturday’s sunrise in Moncton is at 6:10 am and sunset will occur at 8:23 pm, giving 14 hours, 13 minutes of daylight (6:17 am and 8:26 pm in Saint John). Next Saturday the Sun will rise at 5:59 am and set at 8:32 pm, giving 14 hours, 33 minutes of daylight (6:07 am and 8:35 pm in Saint John).

The Moon is full on Sunday, the Mi’kmaq Birds Lay Eggs Moon, and it passes near Jupiter on Monday. Mercury reaches its greatest elongation from the Sun on Monday but it doesn’t get far above the horizon before sunrise on spring mornings due to the shallow angle of the ecliptic. Despite keeping a relatively low profile, Venus dominates the western sky after sunset. Jupiter is now rising around 9 pm and will soon be in the evening sky at sunset. With a small scope you might catch its moon Europa disappearing into Jupiter’s shadow around 10:20 pm on Thursday. Saturn and Mars offer great viewing in the morning sky, with Mars getting much brighter by the week.

The provincial astronomy club, RASC NB, meets at the UNB Forestry / Earth Sciences building in Fredericton this Saturday at 1 pm. The Saint John Astronomy Club meets on May 5 at 7 pm in the Rockwood Park Interpretation Centre. All are welcome to attend either and there is no fee.

Questions? Contact Curt Nason at nasonc@nbnet.nb.ca.

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